The present invention relates to a system for helping to regenerate a catalysed particulate filter arranged in the exhaust line of a motor vehicle diesel engine.
It is known that, generally, filters of this type can be arranged in an exhaust line downstream of an oxidation catalyst on the output side of the engine.
To provide regeneration of a catalysed particulate filter it is necessary to maintain a minimum level of heat of the exhaust gases on the input side thereof, in order to trigger combustion of the particles trapped therein.
This is for example done by post-injecting fuel into the cylinders of the engine.
It is the job of these post-injections to produce a high thermic level of the gases on the output side of the engine, at the same time as ensuring the production of unburned hydrocarbons which are oxidised in the catalyser.
This catalytic oxidation of the hydrocarbons manifests itself in an increase in the thermic level of the exhaust gases on the input side of the filter positioned downstream of the catalyser.
The quantity of unburned hydrocarbons which then passes through the catalysed particulate filter is small and its oxidation by impregnating the catalysed filter does not generate exothermic heat.
It is the object of the invention to propose a system enabling the regeneration of the filter to be speeded up.
To this end, the subject matter of the invention is a system for helping to regenerate a catalysed particulate filter arranged in a motor vehicle diesel engine""s exhaust line, said filter being positioned downstream of an oxidation catalyser on the output side of the engine, characterised in that it includes a gas bypass circuit parallel to the catalyser terminals and fitted with means of controlling the circulation of the gases therein and in the catalyser, in order, at the point when regeneration of the particulate filter is triggered, to divert a proportion of the gases laden with unburned hydrocarbons into the particulate filter without passing via the catalyser, so as to speed up the regeneration of the particulate filter.
Under another feature, the catalyser and the particulate filter are arranged in two separate exhaust line casings.